Bottom Line:
Together, these findings suggest that increased Edn2 expression is protective to mutant PRs.Notably, increased expression of the FGF2 protein in Tg(RHO P347S) PRs was ablated in Tg(RHO P347S); Edn2(-/-) retinas.Our findings indicate that the increased expression of PR Edn2 increases PR survival, and suggest that the Edn2-dependent increase in PR expression of FGF2 may contribute to the augmented survival.

Affiliation: Program in Developmental Biology, The Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada.

ABSTRACTExpression of the Endothelin-2 (Edn2) mRNA is greatly increased in the photoreceptors (PRs) of mouse models of inherited PR degeneration (IPD). To examine the role of Edn2 in mutant PR survival, we generated Edn2(-/-) mice carrying homozygous Pde6b(rd1) alleles or the Tg(RHO P347S) transgene. In the Edn2(-/-) background, PR survival increased 110% in Pde6b(rd1/rd1) mice at post-natal (PN) day 15, and 60% in Tg(RHO P347S) mice at PN40. In contrast, PR survival was not increased in retinal explants of Pde6b(rd1/rd1) ; Edn2(-/-) mice. This finding, together with systemic abnormalities in Edn2(-/-) mice, suggested that the increased survival of mutant PRs in the Edn2(-/-) background resulted at least partly from the systemic EDN2 loss of function. To examine directly the role of EDN2 in mutant PRs, we used a scAAV5-Edn2 cDNA vector to restore Edn2 expression in Pde6b(rd1/rd1) ; Edn2(-/-) PRs and observed an 18% increase in PR survival at PN14. Importantly, PR survival was also increased after injection of scAAV5-Edn2 into Pde6b(rd1/rd1) retinas, by 31% at PN15. Together, these findings suggest that increased Edn2 expression is protective to mutant PRs. To begin to elucidate Edn2-mediated mechanisms that contribute to PR survival, we used microarray analysis and identified a cohort of 20 genes with >4-fold increased expression in Tg(RHO P347S) retinas, including Fgf2. Notably, increased expression of the FGF2 protein in Tg(RHO P347S) PRs was ablated in Tg(RHO P347S); Edn2(-/-) retinas. Our findings indicate that the increased expression of PR Edn2 increases PR survival, and suggest that the Edn2-dependent increase in PR expression of FGF2 may contribute to the augmented survival.

Mentions:
To confirm that Edn2 transcripts are up-regulated in the Prph2rds/+, Tg(RHO P347S), and Pde6brd1/rd1 mouse models of IPD we studied, we measured retinal Edn2 mRNA abundance. As reported by Rattner and Nathans in other models [19], we found the Edn2 mRNA to be greatly increased vs. wild-type (WT) controls in Prph2rds/+ (32-fold), Tg(RHO P347S) (70-fold), and Pde6brd1/rd1 (72-fold) retinas, using qRT-PCR (for each model n = 3; p<0.005) (Fig. 1A).

Mentions:
To confirm that Edn2 transcripts are up-regulated in the Prph2rds/+, Tg(RHO P347S), and Pde6brd1/rd1 mouse models of IPD we studied, we measured retinal Edn2 mRNA abundance. As reported by Rattner and Nathans in other models [19], we found the Edn2 mRNA to be greatly increased vs. wild-type (WT) controls in Prph2rds/+ (32-fold), Tg(RHO P347S) (70-fold), and Pde6brd1/rd1 (72-fold) retinas, using qRT-PCR (for each model n = 3; p<0.005) (Fig. 1A).

Bottom Line:
Together, these findings suggest that increased Edn2 expression is protective to mutant PRs.Notably, increased expression of the FGF2 protein in Tg(RHO P347S) PRs was ablated in Tg(RHO P347S); Edn2(-/-) retinas.Our findings indicate that the increased expression of PR Edn2 increases PR survival, and suggest that the Edn2-dependent increase in PR expression of FGF2 may contribute to the augmented survival.

Affiliation:
Program in Developmental Biology, The Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada.

ABSTRACTExpression of the Endothelin-2 (Edn2) mRNA is greatly increased in the photoreceptors (PRs) of mouse models of inherited PR degeneration (IPD). To examine the role of Edn2 in mutant PR survival, we generated Edn2(-/-) mice carrying homozygous Pde6b(rd1) alleles or the Tg(RHO P347S) transgene. In the Edn2(-/-) background, PR survival increased 110% in Pde6b(rd1/rd1) mice at post-natal (PN) day 15, and 60% in Tg(RHO P347S) mice at PN40. In contrast, PR survival was not increased in retinal explants of Pde6b(rd1/rd1) ; Edn2(-/-) mice. This finding, together with systemic abnormalities in Edn2(-/-) mice, suggested that the increased survival of mutant PRs in the Edn2(-/-) background resulted at least partly from the systemic EDN2 loss of function. To examine directly the role of EDN2 in mutant PRs, we used a scAAV5-Edn2 cDNA vector to restore Edn2 expression in Pde6b(rd1/rd1) ; Edn2(-/-) PRs and observed an 18% increase in PR survival at PN14. Importantly, PR survival was also increased after injection of scAAV5-Edn2 into Pde6b(rd1/rd1) retinas, by 31% at PN15. Together, these findings suggest that increased Edn2 expression is protective to mutant PRs. To begin to elucidate Edn2-mediated mechanisms that contribute to PR survival, we used microarray analysis and identified a cohort of 20 genes with >4-fold increased expression in Tg(RHO P347S) retinas, including Fgf2. Notably, increased expression of the FGF2 protein in Tg(RHO P347S) PRs was ablated in Tg(RHO P347S); Edn2(-/-) retinas. Our findings indicate that the increased expression of PR Edn2 increases PR survival, and suggest that the Edn2-dependent increase in PR expression of FGF2 may contribute to the augmented survival.